Shackle-type padlocks having latch bolts spring-biased into locking engagement with a retaining notch formed in a leg of the shackle, to secure the shackle in locked condition into the padlock casing, have frequently been subjected to forceful and manipulative tampering schemes to open these padlocks. In many prior designs of such padlocks, such as the patents to Soref et al. U.S. Pat. Nos. 2,113,864; 2,487,608; 2,893,231; and Markert et al. U.S. Pat. No. 3,194,033, in which a spring-biased latch bolt slidably carried in a rocker secures the shackle in a locked position, intruders have discovered that cyclic or repetitive, continued force delivered to the shackle and transmitted to the latch bolt through the inclined face of the locking notch of the shackle, and the inclined face of the nose of the latch bolt could produce a reciprocating or vibratory motion of the latch bolt, brought into play by the elastic restoring force of the spring biasing the latch bolt into engagement with the shackle.
Where the reciprocating motion of the latch bolt produces a harmonic motion in the spring, and particularly where the rocker may have play, a progressively increased degree of reciprocation of the latch bolt is possible without a comparative increase in motion of the shackle, which is obviously restricted by the latch bolt. This has been achieved by continued tapping in synchronism with the natural frequency of the spring, whereby the elastic restoring force is reinforced by the impacts of the cyclic tapping force to a point where the latch bolt will "bounce" completely out of locking engagement with the shackle, whereupon the padlock can be opened.
The present invention, while providing the usual security associated with this type of lock, also overcomes the above-described deficiencies and short-comings relative to prior spring-biased latch bolt padlocks, by mounting the latch bolt for reciprocable movement in a pivoted rocker accommodating release of the latch bolt by the usual permutation or key-operated mechanism, and by providing the rocker with an arcuate face struck about the axis of pivotal movement of the rocker, and slidably engaging a stabilizing fin extending inwardly from the lock casing, and with a stop segment limiting movement of the rocker in a release direction and cooperating with the latch bolt to limit inward movement of the shackle. The fin and segment cooperate to retain the rocker from vibratory motion as well as relieve the pivot for the rocker from excess shear. The latch bolt has a face converging toward its nose and forming a notch engaged with the face of the rocker facing the short leg of the shackle, and limiting retractable movement of the latch bolt as release of the shackle is attempted by forceful pulling on the shackle.
An advantage of the present invention, therefore, is in the stabilizing means and stop for the rocker and shackle for a permutation-type padlock which overcomes the deficiencies and short-comings of the prior art.
A further advantage of the present invention is in the simplicity and effectiveness of the safeguard means to solve the deficiencies of spring-biased latch bolts.
Still another advantage of the invention resides in the cooperation between the safeguard means and the key cylinder release mechanism.
A still further advantage of the invention resides in the relief of the pivot pin for the rocker from excess shear.
Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure.